In my previous post I showed an adjustable step-down configuration of AX3003 (SMD buck converter salvaged from old electronic equipment ) and i was wondering what would it take to turn it into a boost converter when I found this paper http://www.ti.com/lit/an/slyt286/slyt286.pdf
It shows how to use a buck converter in an inverting buck-boost topology.
Important note: The paper calls for connecting the Vss pin of the buck device to Vout but if i keep the Vss pin floating (not connected) and connect the Feedback network to Vin instead of Vout, the output voltage goes over -50V !!! (serious boost)!